Biologic scaffold materials composed of extracellular matrix (ECM) have been derived from a wide variety of xenogeneic and allogeneic tissue and organ sources. These materials have been used in a similarly wide variety of pre-clinical and clinical tissue engineering and regenerative medicine approaches to tissue reconstruction. When prepared and utilized appropriately, ECM scaffolds have been shown to promote the formation of functional, site-specific host tissues. This is in direct contrast to the default mammalian host response to tissue injury, which involves inflammation and scarring. The exact mechanisms by which ECM scaffold materials are capable of modulating the default host response and promoting this type of constructive tissue remodeling are largely unknown. However, we have shown that those ECM scaffolds that are capable of promoting constructive remodeling are also associated with a distinct population of macrophages within the site of implantation. A number of changes in macrophage physiology have been observed to occur with advanced age. These changes have been associated with an inability to fight pathogens and to heal wounds. The exact mechanisms which underlie these changes are unclear, but have been suggested to include alterations in the local tissue microenvironment (i.e. ECM composition, and resident cell populations) which contribute to anergic macrophage behavior. The proposed work seeks to investigate the response of macrophages derived from young, adult, and aged mice following interactions with biologic scaffold materials composed of ECM derived from young, adult, and aged porcine donors (Aim 1). Further, the proposed work seeks to identify the ligands responsible for macrophage-ECM scaffold interactions and assess the relative presence of these ligands in ECM scaffold materials derived from young-adult and aged donors (Aim 2). These goals will be accomplished by experienced investigators through a set of in vitro studies which utilize state of the art high throughput methodologies. The completion of these studies will not only further the understanding of the mechanisms by which ECM scaffolds modulate the host response, but will also lead to a better understanding of the impact that the changes in macrophage physiology which occur with aging will have upon the potential to utilize regenerative medicine strategies in an aging population.